The purpose of the project is to determine the incidence rates, rates of progression, and risk factors for the chronic complications of NIDDM. The study is conducted in the Pima Indians of the Gila River Indian Community, who have participated in a longitudinal epidemiologic study since 1965 (see project Z01 DK 69000). Risk factors for the major complications of diabetes, retinopathy, nephropathy, coronary artery disease, and peripheral vascular disease are determined by longitudinal followup of diabetic subjects. Methods of ascertainment of these complications include fundus photography, measurement of urine albumin and serum creatinine concentrations, electrocardiography, and documentation of lower extremity amputations. Retinopathy and other retinal lesions were assessed by ophthalmoscopy and fundus photography in 288 nondiabetic and 1074 diabetic Pima Indians. Fundus photography was more sensitive in detecting nonproliferative and proliferative retinopathy. Retinopathy was strongly related to the duration of diabetes and to type of diabetes treatment, with the highest prevalence in insulin-treated patients. The relationships between glycated hemoglobin (HbA1), fasting and two-hour post-load plasma glucose concentrations, and diabetic retinopathy were examined, and the strengths of the associations were directly compared by receiver operating characteristic analysis. All three measures of glycemia were highly associated with each other and with either the prevalence or incidence of retinopathy. HbA1 was slightly, but not statistically significantly, more closely related to diabetic retinopathy than a single plasma glucose determination.